Climbing Stairs

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

分析：这道题就相当于青蛙跳，就是一个费波那契数列。如果只有1级台阶，那显然只有一种跳法，如果有2级台阶，那么有两种跳的方法了:一种分两次条，每次跳一个；另外就是一次跳2级。我们把n级台阶的跳法看成是n的函数记为f(n)。当n>2时，f(n)=f(n-1)+f(n-2);

class Solution {
public:
    int climbStairs(int n) {
        int result[2]={1,1};
        if(n<2)
            return result[n];
        int fibN=0;
        int fibOne=1;
        int fibTwo=1;
        for(unsigned int i=2;i<=n;++i)
        {
            fibN=fibOne+fibTwo;
            fibOne=fibTwo;
            fibTwo=fibN;
        }
        return fibN;
    }
};